Effects of arginine and protein on chicks' responses to dietary lysine.

1. A chick experiment was designed to test whether the proven effect of excess protein on the requirement for lysine was associated with the arginine content of the protein. 2. Protein contents of 180, 220, 260 and 300 g/kg diet were fed in combination with lysine concentrations of 38, 43, 48, 53 and 58 g/kg crude protein and arginine concentrations of 49.4 or 68.4 g/kg crude protein. 3. Growth rate and efficiency of food utilisation were not significantly affected by the arginine content of the protein. Significant responses to lysine were obtained at all protein contents. 4. Lysine required for maximum growth or maximum food efficiency increased in direct proportion to the protein content of the diet and was not affected by arginine content of the diet within the range of concentrations tested.